In the conventional chain saw the crankcase of the prime mover is molded integral with the body which is generally made of a magnesium die-casting or similar material, and a handle frame is fitted through vibration dampening members or a guide bar structure to the body.
In such conventional chain saws several following problems have been encountered. Although the crankcase is required to be of high precision, the integral molding of the crankcase with the body makes the chain saw so large that a magnesium die-casting or the like is difficult to form and work, as a result of which the device becomes quite expensive.
While it is necessary to modify the shape and size of the body for each of the various chain saw models, the engine itself does not have to be modified to provide the required operational performance. Consequently, intergration of standard engines with standard bodies is not possible, and special moldings must be made each respective model.
Further, since the crankcase and the body are integral, the engine cannot be assembled in advance, and the manufacturing efficiency is low.